1. Field of the Invention
The present invention relates to a fluid coupling including a socket and a plug.
2. Description of the Related Art
FIG. 13 shows a state where a plug 1 and a socket 2 in a conventional fluid coupling as described in Japanese Unexamined Patent Publication No. 2002-295770 are assembled with each other, and FIG. 14 shows a state where the plug 1 and the socket 2 are separated from each other.
As shown in FIG. 13, the plug 1 and the socket 2 have shapes of cylinders in which flow paths are formed on inner surfaces. On the inner surface of one end of the plug 1 is formed a female screw 3, to which one of pipes is connected by screw joint. A screw ball engaging outer circumferential groove 6 is formed on a center of an outer circumference of the plug 1.
The socket 2 includes a main body portion 7 on a right side in FIG. 13 and a plug insertion portion 8 on a left side therein. Symmetrically to the plug 1, on the inner surface of one end of the main body portion 7 is formed a female screw 9, to which the other pipe is connected by the screw joint.
In the vicinity of an opening end (left end in FIG. 13) of the plug insertion portion 8 of the socket 2, a stopper 8a is formed on an outer surface thereof, and steel balls 13 are housed in a plurality of holes 12. On an inner circumferential groove 14 formed on a center of an inner surface of the plug insertion portion 8, an O-ring 15 is mounted. On an outer circumferential surface of the plug insertion portion 8, a sleeve 16 is fitted, and is biased toward the opening end (left end in FIG. 13) by a spring 17.
As shown in FIG. 14, a valve 19 housed in an inside of the plug 1 includes a valve main body portion 22 that abuts against a valve seat 4 of the plug 1, a protruding portion 23 that protrudes outward of an opening end of the plug 1 from the valve main body portion 22, and a valve guide 24 that protrudes inward of the plug 1 from the valve main body portion 22.
In a cylindrical portion 28 that forms a part of a valve holder 20, the valve guide 24 of the valve 19 is inserted so that the valve 19 is supported slidably in an axial direction thereof.
A spring 21 biases the valve main body portion 22 of the valve 19 so that the valve main body portion 22 abuts against the valve seat 4.
In order to perform a coupling action to the conventional fluid coupling configured as described above, first, the sleeve 16 of the socket 2 is moved in a direction of an arrow A as shown in FIG. 14. When the plug 1 is inserted into the plug insertion portion 8 of the socket 2 in this state, the steel balls 13 of the socket 2 are retreated to the inner circumferential groove 18 of the sleeve 16, and accordingly, the plug 1 can be inserted into the plug insertion portion 8 of the socket 2. When the plug 1 is inserted to a deep portion of the plug insertion portion 8 of the socket 2, the protruding portion 23 of the valve 19 of the plug 1 presses the protruding portion 23 of the valve 19 of the socket 2. In such a way, as shown in FIG. 13, the valve 19 of the plug 1 and the valve 19 of the socket 2 are retreated by pressing each other, and it becomes possible to move a fluid therebetween. When the sleeve 16 is returned in a direction reverse to the direction of the arrow A, the steel balls 13 leave the inner circumferential groove 18 and are pressed by the inner circumferential surface of the sleeve 16 to protrude from an inner surface of the socket 2. Then, the steel balls 13 are engaged and locked with the outer circumferential surface of the plug 1. In such a way, the plug 1 is inhibited from leaving the plug insertion portion 8 of the socket 2.
In order to release the coupling between the plug 1 and the socket 2, the sleeve 16 is moved in the direction of the arrow A from the state shown in FIG. 13, and the plug 1 is pulled in a leaving direction. Then, the steel balls 13 are retreated to the inner circumferential groove of the sleeve 16, whereby the plug 1 can be pulled out. When the plug 1 leaves the socket 2, the valves 19 of the plug 1 and the socket 2 individually move forward by being biased by the springs 21, and are brought into pressure contact with the valve seats 4 and 10. Then, the opening ends of the plug 1 and the socket 2 are closed so as to seal the fluid, and sealing by the O-ring 15 between the plug 1 and the socket 2 is also released. As a result, the plug 1 and the socket 2 can be detached from each other without causing fluid leakage.
In a fluid coupling of a pipe system, it is ideal in terms of ensuring a flow rate without causing a pressure loss that a diameter of a flow path thereof is not changed in order to have a fixed cross-sectional area, and a flowing direction of the fluid is constant. However, in the conventional fluid coupling, as shown in FIG. 15, the fluid that has flown in from an inlet path a of the plug 1 passes through the valve holder 20 (flow path b) of the plug 1, the spring 21 (flow path c), an outer diameter portion (flow path d) of the valve 19, a narrow portion (flow path e) of the valve 19, and a boundary portion (flow path f) between the plug 1 and the socket 2. Then, the fluid further passes through a narrow portion (flow path g) of the valve 19 of the socket 2, an outer diameter portion (flow path h) of the valve 19, the spring 21 (flow path i), and the valve holder 20 (flow path j), and then flows out from an outlet path k. The fluid coupling has such a complicated route, and accordingly, the cross-sectional area and the flowing direction are changed, resulting in the pressure loss.
Since the fluid coupling has such complicated flow paths, it is necessary to allow some pressure loss. However, the market desires a fluid coupling with a low pressure loss, in which a flow path resistance of each portion is small and a larger flow rate can be ensured.
In view of the above, a fluid coupling shown in FIG. 16 is proposed. In this fluid coupling, there is provided, between each valve 33 and each valve holder 31, a conic coil spring 32 that has an outer diameter gradually changed according to a conic shape along a line connecting an outer diameter portion of the valve 33 and an outer diameter portion of the valve holder 31 when the valve 33 of the plug 1 and the valve 33 of the socket 2 abut against each other and each spring 32 is compressed.
With such a configuration as described above, reduction and increase of the flow, which have occurred heretofore due to differences in height among the flow paths, are eliminated, and there is no collision of the fluid or occurrence of a swirl, and thereby the pressure loss can be reduced. Moreover, an effective opening area of the fluid coupling is large, and flow path resistances of the plug and the socket are reduced to a great extent, and thereby the pressure loss occurring when the fluid is flown at the same flow rate can be reduced.